Parallel flow hemodialyzer

ABSTRACT

A hemodialyzer with semipermeable membrane tubes arranged in parallel. The tubes lead to dialysate manifolds at either ends of the tubes which are sealed from blood manifolds one on each side of the tubes by epoxy resin surrounding each cellophane tube. The tubes are closely packed with dialysate flowing through them and blood flowing around them. Tube supports within the tubes provide flow paths for both the dialysate and the blood while flaps on the outside of each tube prevent peel stress due to blood flow from destroying the epoxy bonds.

United States Patent [72] Inventors Ardis R. Lavender 3,228,877 1/1966 Mahon 210/321X North Riverside; 3,362,540 1/1968 Bluenile, Jr 210/321 Finley W. Markley, Naperville, 111. OTHER REFERENCES 5; H 3 5 2 Kolff, w. J. Dialysis Becomes Practical," a publication of l 1 m C. H. Boehringer Sohn, lngelheim Am Rhein, pp. 4, 19, 27, [45] Patented Feb. 23, 1971 34 36 and 37 relied on [73] Assignee the United States of America as represented by the United States Atomic Energ Primary Examiner-Frank A. Spear, Jr. Commission Att0rneyRo1and A. Anderson [54] PARALLEL FLOW HEMODIALYZER 3 cl i 6 D i Fi ABSTRACT: A hemodialyzer with semipermeable membrane 8 I tubes arranged in parallel. The tubes lead to dialysate U. u C I s s s v e s s s s s s s s s s s s s s s s 1 blood manifolds one on each side of the tubes by epoxy resin [5 1 e 0 earc surrounding each cellophane albe- The tubes are closely 23/25 packed with dialysate flowing through them and blood flowing around them. Tube supports within the tubes provide flow [56] ggfiif: i NT paths for both the dialysate and the blood while flaps on the U S A E s outside of each tube prevent peel stress due to blood flow 2,664,395 12/1953 Marchand 210/321 from destroying the epoxy bonds Z6 "ates-=1? 515 .'=i

t 'fff igga poooooooosq" I8 28 ,ZZ 26 PALLEL FLOW HEMODIALYZER CONTRACTUAL ORIGIN OF THE INVENTION The invention described herein was made in the course of,

or under, a contract with the UNITED STATES ATOMIC This invention relates to an apparatus and method for extracorporeal hemodialysis and more particularly to hemodialysis with a small disposable unit usable in the home.

Hemodialysis is a proven and life saving therapy for people with chronic renal failure. At the present time, hemodialysis is costly, time-consuming and complex. Hemodialysis for each patient usually costs from $10,000 to $25,000 per year and requires skilled medical and technicalpersonnel and also occupies valuable hospital bed space. It has been estimated that an annual increment of 50,000 people each year would benefit from hemodialysis therapy if it were economically and technically feasible, but at the present time,only about 900 persons are receiving treatment in the United States.

A common type of machine used for hemodialysis consists of a tightly wound cellophane tube submerged in a dialysate. Blood containing various amino impurities such as urea and creatinine as well as excessive amounts of sodium chloride and other salts passes through the cellophane tube. Since the concentration of the various impurities in the blood is greater than the concentration of the impurities in the dialysate, a concentration gradient is established across the cellophane. The cellophane acts as a semipermeable membrane through which the impurities may pass but not the blood. Since the cel lophane tube is long and tightly 'wound, a blood pump is required to force blood through the tube. The blood in the tube is under greater pressure than the dialysate so a pressure gradient in addition to the aforementioned concentration gradient exists across the cellophane tube. The pressure gradient is a driving force which forces water from the blood into the dialysate. The blood is at greater pressure than the dialysate for two reasons: first, transfer of water from the blood is a renal function; and second, the greater pressure of the blood prevents contamination of the blood by dialysate if there is a leak in the tube.

The machine has several disadvantages with respect to home use. Because the pressure drop from one end to the other of the cellophane tube is long, a blood pump is necessary to force blood through the tube. Blood clots may result from use of the pump and care must be taken to prevent their formation. In addition, the blood inventory in the cellophane tube is substantial and a transfusion often is required when the machine is used. Only part of this blood can be recovered from the machine and since blood is expensive, this represents a significant cost in hemodialysis. It is clear that the machinery necessary for hemodialysis is not only complicated and expensive, but the required transfusions and blood pump prevent its use by anyone other than trained medical personnel. All these factors in addition to the limited amount of available hospital space result in people dying every year because hemodialysis is not available to them.

The dialyzer of this invention is related to that described in copending application Ser. No. 722,445. The applicants for both inventions are the same, and the inventions are related in that both concern dialyzers which make use of a plurality of short parallel semipermeable membrane tubes. In both inventions, the blood is under greater pressure than the dialysate in order to ensure that water transferas well as impurity transfer occurs. In the first filed invention, great care was required to prevent the blood from contacting sharp surfaces and to that end, considerable detail was devoted to providing rounded surfaces at the blood inlet. Steps included in providing rounded surfaces were the introduction of inserts into the cellophane tubes, two different potting steps and shims to reduce the volume of blood not in contact with the cellophane tubes. The present invention obviates the necessity for the intricate manufacturing steps required in the prior invention by reversing the flow paths of the dialysate and the blood so that the dialysate flows inside the tubes while blood flows across the tubes. The reversal of the dialysate and blood flow paths in the present invention gives rise to a significant simplification of the manufacturing procedures required for the device, as will be explained.

It is the principal object of this invention to provide a small disposable hemodialyzer which may be used for the purification of blood by nonmedically trained personnel.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal section of a device according to the invention.

FIG. 2 is a partial section taken along line 2-2 of FIG. 1.

FIG. 3 is a partial section taken along line 3-3 of FIG. 2.

FIGS. 4 and 5 are enlarged views of different embodiments of the invention.

FIG. 6 is a section of a species of support members.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIG. 1, dialyzer 10 is comprised of a rectangular housing 11 including parallel sides 12 and 13 and ends 14 and 15. Connected to housing 11 through end 15 is a dialysate inlet 16 and through end 14 a dialysate outlet 17. Also connected to the housing through side 13 is a blood inlet 18 and through side 12 is a blood outlet 19. A plurality of semipermeable membranes in the format elongated, flat cellophane tubes 20, each containing a nonwoven plastic mesh support 21, are disposed in parallel relationship within housing 11. Cellophane tubes 20 are slightly smaller than is housing 11 thereby providing room for a dialysate inlet manifold 22 with which dialysate inlet 16 communicates, a dialysate outlet manifold 23 with which dialysate outlet 17 communicates, a blood inlet manifold 24 with which blood inlet 18 communicates and a blood outlet manifold 25 with which blood outlet 19 communicates. A layer 26 of epoxy resin between the housing and the cellophane tubes on each side of the housing at the top and bottom thereof seal the inlet manifolds from the outlet manifolds and create a blood chamber between the dialysate inlet and outlet.

With reference also to FIG. 2 it is seen that each cellophane tube 20 has at each end and on each side of the tube, foldedback flaps 27 which have a tapered and rounded edge 28, the purpose of which will be later explained. Any epoxy resin head 29 seals each and every flap 27 to the flap of the next cellophane tube 20. The epoxy resin bead 29 is placed at a point on flap 27 to ensure a complete seal across the width of tubes 20.

FIG. 3 shows in more detail the character of nonwoven mesh support 21 which is preferably as thin as possible. The mesh support 21 must be nonwoven in order to provide paths for blood flow resulting from deformation of the cellophane tubes 20 into the interstices of the mesh due to the pressure gradient between the blood and dialysate.

FIG. 6 shows an alternate form of mesh support 2!. The support consists of a thin plastic sheet formed into alternately inverted hollow pyramids or cones 31 arranged so that an upward pointing pyramid 32 is surrounded on four sides by downward pointing pyramids 33. These support members are also described in the aforementioned related application.

In operation, blood enters blood inlet 18 and flows into blood inlet manifold 24. The blood flows across cellophane tubes 20 into blood outlet manifold 25 and thereafter out of dialyzer 10 through blood outlet 19. The dialysate enters dialysate inlet 16 and flows from dialysate inlet manifold 22 through cellophane tubes 20 to dialysate outlet manifold 23 and out of the dialyzer 10 through dialysate outlet 17. Although the flow paths of both the blood and the dialysate have been reversed from those shown in out application Ser. No. 722,445, it will be shown, with data hereinafter reported,

that the pressure drop between the blood inlet 18 and the blood outlet 19 remains negligible and the blood-priming volume or inventory is in fact smaller than the related invention hereinbefore mentioned. Since the blood inventory in the dialyzer is small and the pressure drop between the blood inlet 18 and the blood outlet 19 is negligible, neither transfusions nor blood pumps are required.

Since the blood is at higher pressure than dialysate in order to drive water from the blood to the dialysate, the cellophane tubes 20 deform around mesh supports 21 as shown in FIGS. 4 and 5. It is this deformation of tubes 20 into mesh 21 that provides a path for the blood to flow since the assembly of tubes is compressed until the distance between the tubes is theoretically zero. Additionally, the absence of inserts in the tubes a s required in our first filed invention obviates the necessity of shims to increase the amount of blood in contact with tubes 20. In FIG. 4 cellophane tubes 20 are bonded to each other at either end by epoxy resin bead 29 without the use of flaps 27. Dialysate flow is represented by arrows 34 while blood flow is either into or out of the paper. There is, however, pressure exerted by the blood in the direction of arrows 35. Because cellophane tubes 20 are deformed at the juncture 36 of the tube and the epoxy resin bead 29 due to the pressure gradient between the dialysate and the blood, the blood will exert a peel stress against the tube at the juncture which causes the tube to peal away from the bead and result in failure of the sea]. This peel stress is principally caused because of the difference in pressure between the blood and the dialysate at juncture 3. Referring now to FIG. which shows the preferred embodiment, if nonwoven mesh supports 21 are employed inside cellophane tubes 20, it is seen that folded-back flaps 27 are bonded to each other by epoxy resin bead 29 so that there is no pressure gradient across the cellophane tube at the juncture 37 of the epoxy bead and the flaps because blood is present on both sides of the flap; the absence of the pressure gradient results in no appreciable peel stress on the epoxy resin bead. Friction between the fiap and its adjacent tubes prevents motion of the epoxy bead 29 under influence of the 9 blood pressure and therefore, peel stresses on the opposite side of the epoxy cellophane juncture are also prevented. The use of flaps 27 result in a seal which is permanent within the testing experience of this device while devices prepared with mesh supports 21 but without flaps 27 have failed within an hour and a half of the start of tests.

It is contemplated that flaps 27 will not be needed if the alternate support member 30 is used since pyramids 31 are so creatinine, sodium chloride and other salts. In all experiments the blood flow rate and the dialysate flow rate were recorded in milliliter per minute. Blood samples were taken, analyzed and the dialysance of various impurities calculated. Di-

alysance in milliliter per minute is defined as A-V m) X blOOd fiOW rate where: w A concentration of impurity in blood entering dialyzer;

V concentration of impurity in blood leaving dialyzer; and

D concentration of impurity in dialysate entering dialyzer.

All experiments were conducted at room temperature and except for the experiments with dogs, the blood flows and dialysate flows were adjusted with constant flow pumps. The data obtained from these experiments are presented in the following experiments:

EXPERIMENT 1 In vitro-Saline Solutions DFl Dialysance (ml./min.)

(ml./n1in.) (mL/rnin.) Urea Creatinine Na K DE=DiaIysate flow.

EXPERIMENT II Pressure drop at 600 m1./min.=4 mm. Hg. Priming vo1ume=15 ml. Surface area=0.5558 square meter.

65 tubes; 9 cm. length x 4.5 cm. width.

In Vitro-Saline Solutions Dialysance (mL/min.)

BF( DF( (mI./min.) (mL/min.) Urea Creatlnine Na K (b) DF=Dialysate flow.

EXPERIMENT r11 EXPERIMENT V-Continued Pressure drop at 612 m1 /mm'=12 mm Hg Pressure drop at 600 n1l./min.=10 mm. Hg priming vo1ume=9 Pruning volnme=20 ml. Surface area=0.54 square meter 80 tubes; 7.5 cm. length x 4.5 cm. width In 1troSa11ne Solutions r- 4 Dialysance ml. min. In 1 mo Saline Solutions BF (8) DF (b) Dialysance (ml./min.) (ml./min.) (ml./min.) Creatinine Na K BF (2) DF( c (ml./min.) (ml./min.) Urea Greatmme N a K 300 120 25 50 56 300 267 24 50 57 144 132 47 46 32 41 300 384 29 50 63 144 300 55 45 32 53 300 540 38 55 70 144 480 61 46 36 57 300 924 37 56 73 144 53s 62 48 40 62 144 672 48 45 44 61 4 3 114 25 52 52 468 234 23 56 55 276 132 49 32 51 4 3 39 30 52 5 276 324 60 62 43 59 468 552 41 55 72 276 468 73 69 54 63 1 5 4 924 45 7 4 276 576 78 66 52 65 276 768 75 64 52 68 600 114 17 39 47 600 240 19 51 52 450 132 45 59 3s 61 600 384 26 52 65 450 252 43 59 41 68 00 552 32 59 72 450 432 68 59 41 77 00 744 34 59 77 450 636 61 63 43 79 00 3g 3 62 84 450 768 60 68 53 84 450 900 51 51 59 86 (a) BF=Blood flow. (b) DF=Dialysate flow. 612 132 37 47 64 69 612 312 61 52 42 71 EXPERIMENT V1 612 480 63 57 49 79 612 624 76 67 62 84 Pressure drop at 618 m1./min.=12 mm. Hg 612 768 78 80 83 83 Priming volume=50 ml.

. Surface area=0.75 square meter BF=Blood flow. Dialysa fl 1 64 tubes; 13 cm. length x 4.5 cm. width A 7 In Vino-Saline Solutions EXPERIMENT IV DF Dialysance (ml/min.)

, B 5) 5) e at 624 Hg (mL/min.) (ml/min.) Oreatinine Na K Priming v0lu1ne=27 ml. Surface area=0i6048 square meter 492 144 40 46 50 In Vitro-Saline Solutions g3 Dialysance (mL/min.) BF 6) DF 492 960 52 73 97 (ml/min.) (mL/min.) Urea Creatuune Na K 44 49 59 64 144 144 37 21 29 28 ion 39 70 84 144 228 34 26 32 47 618 456 53 72 85 144 38 27 36 50 618 600 42 75 34 144 37 32 54 618 792 52 33 97 144 46 34 55 618 912 35 67 87 144 39 23 29 40 a 53g 240 52 25 39 B F -Blood flow. DE D1alysate flow. 288 336 60 38 2g 22 444 58 23 696 70 32 5s 72 we claim 2 32 47 45 1. A hemodlalyzer comprising a housing having at one end a :22 gig g} 42 53 dialysate inlet leading to a dialysate inlet manifold and at the 456 336 58 2% 2 2% other end a dialysate outlet leading from a dialysate outlet :22 gag g 42 62 48 manifold; a blood chamber having a blood inlet manifold and 04 34 37 a blood outlet manifold between said dialysate inlet and outggi g 5 64 49 let, said blood chamber being sealed from said dialysate inlet 2; 360 46 if; g; g; manifold and outlet manifold; a plurality of semipermeable $3 3 41 63 71 membranes in the form of parallel tubes extending through the 24 696 44 41 69 7 blood chamber and sealingly connecting the dialysate inlet a =B1 d fl (b) DF=D4 t flow. manifold and outlet manifold; said tubes having on both sides BF o0 ow 1a ysa e and on each end folded-back flaps, said flaps being generally curved at one end and forming an opening at the other end for EXPERIMENT V dialysate flow, the greater dimension of said opening being es- Pressure drop at 600 r11l./min.=10 mm. Hg Sentially normal to the longitudinal axis of the cellophane Priming v0111me=20 tube; and a blood inlet and outlet connected to the respective In vitm sanue solutions blood inlet and blood outlet manifolds.

The embodiments of the invention in which an exclusive BF (:1) 1 5) Dmlysance (mL/mm) property or privilege is claimed are defined as follows: n-) l-l ea n Na K 2. The dialyzer of claim 1 wherein the tubes are sealed to 138 120 19 30 36 each other with epoxy resin on the flaps at a point near the 128 330 g5 g2 tube openings. 2 41 5 3 The dialyzer of claim 1 wherein the tubes are cellophane 138 966 35 6 65 and have a wall thickness of about 1 mil. 

2. The dialyzer of claim 1 wherein the tubes are sealed to each other with epoxy resin on the flaps at a point near the tube openings.
 3. The dialyzer of claim 1 wherein the tubes are cellophane and have a wall thickness of about 1 mil. 